This invention relates to connectors for temporarily sealing the end of tubes and conduits and pressurizing the tubes for testing to be sure that the tubing does not leak. Recently, to increase the surface area of copper tubing used in the refrigeration industry, a "Rifle ID" feature has been included. This feature involves a knurling operation which is performed on the inner diameter of the tubing. Problems have been encountered with the sealing devices used when pressure testing the components that utilize this copper tubing. Previous devices have utilized an O-ring seal which provides inadequate sealing at high pressures and minimal seal life, due to the high internal pressure and the grooved inner diameter. Sealing on the outer diameter of the copper tubing has provided unsatisfactory results because the OD of the tube is not controlled to a sufficient tolerance to allow for consistent sealing.